In a frying pan over medium heat, cook the bacon until crispy, about 8-10 minutes. Once done, remove and let it drain on a paper towel, then crumble into pieces.
In a large mixing bowl, combine the mixed greens, blackberries, cherry tomatoes, red onion, and walnuts (if using).
In a separate small bowl, whisk together the olive oil, balsamic vinegar, salt, and pepper until well combined.
Drizzle the dressing over the salad mixture and toss gently to coat all the ingredients evenly.
Add the crumbled bacon and blue cheese on top of the salad.
Serve immediately on salad plates, giving a final sprinkle of salt and pepper if desired.
For extra crunch, you can toast the walnuts before adding them to the salad.
If you prefer a sweeter dressing, add a teaspoon of honey to the vinaigrette.